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Biosorption Characteristics And Mechanism Of Stenotrophomonas Sp. On Uranium-containing Wastewater

Posted on:2021-12-16Degree:MasterType:Thesis
Country:ChinaCandidate:L L ZhengFull Text:PDF
GTID:2480306110459564Subject:Environmental Science and Engineering
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Microorganism biosorption has become the research focus of radioactive uranium pollution remediation due to its advantages such as high efficiency,safety and economy.In this research,Stenotrophomonas sp.CICC 23833,a bacterium with high tolerance to uranium,was selected and its growth characteristics,uranium biosorption behavior and uranium biosorption mechanism were studied.The following main research results have been obtained:(1)The bacteria Stenotrophomonas sp.CICC 23833 has a strong tolerance to uranium.The ambient pH and shaking speed have a greater impact on the growth and metabolism of the bacteria.Under the initial uranium concentration of 50 mg/L,the optimal growth conditions of the bacteria are:pH 5?8,temperature 30?40?,speed 250 rpm.(2)Under the conditions of providing nutrients,Stenotrophomonas sp.CICC 23833 has a good biosorption capacity for uranium,and its biosorption efficiency is related to the initial uranium concentration,pH,and the sterilization time of LB medium and so on.The optimal conditions for bacteria to adsorb uranium are:pH 5?7,temperature 25?35?,and 10%inoculation volume.Under these conditions,the biosorption rate of uranium by bacteria can reach more than 97%.The coexisting cations Al3+,Fe2+and Fe3+can inhibit the growth of bacteria and uranium adsorption,among which Al3+is the most influential.(3)The pH of the solution has a great influence on the biosorption of uranium by the cells.The optimal biosorption conditions for the cells are:pH 6,temperature 35?40?,and the cells'biosorption capacity of uranium can reach 198.9 mg/g(dry weight)when the cells density is 0.2 g/L.With the increase of cell concentration in the system,the uranium biosorption rate of cells increased from 30.6%to 72.2%;with the increase of the initial uranium concentration,the uranium biosorption capacity increased from 43.3 mg/g(dry weight)to 392.6 mg/g(dry weight).(4)The biosorption of uranium by the live cells and inactivated cells is similar.The biosorption process is mainly divided into two stages.The first stage is rapid biosorption,which mainly occurs in the first 0.5 h.The amount of uranium adsorbed by inactivated cells is higher than that of live cells.The second stage is the slow biosorption,and the biosorption gradually reaches equilibrium,and the biosorption capacity of live cells at the equilibrium end point is higher than that of the inactivated cells.(5)The Freundlich equation can describe the process of uranium biosorption by cells well,indicating that the biosorption of uranium by cells is a heterogeneous biosorption process.In addition to cell surface adsorption,there may be other biological mechanisms such as intracellular accumulation.The Pseudo-second-order model can better simulate the entire biosorption process,indicating that the uranium biosorption capacity of the cells depends on the available active sites of the bacteria,the concentration and properties of uranium in the solution.(6)SEM-EDS,TEM,XRD and XPS were used to study the biosorption mechanism of uranium by Stenotrophomonas sp.CICC 23833.The results showed that the surface of the cells was rough after the biosorption,and agglomerated into clusters.A large number of black particles appeared in the cells and the chemical composition of the bacteria including UO3?UOCl2?UO2Cl2?(UO22)(P6O17)and other substances,it shows that Stenotrophomonas sp.CICC 23833 may have electrostatic adsorption,chelation and intracellular accumulation of uranium.
Keywords/Search Tags:Uranium contaminated wastewater, Stenotrophomonas sp. CICC 23833, Biosorption
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